The benefit of using zebrafish (Danio rerio) models as part of an integrative approach to improve human health is being realized by the scientific community, with 800 laboratories, supported by some 735 grants from NIH using this fish model. As with any animal model, infections can compromise research by causing high mortalities and subclinical infections compromise research by inducing non-protocol induced variation. Third, Mycobacterium spp. that have been reported from zebrafish are all recognized human pathogens, and thus fish with these infections present human health concerns. Therefore, as with other models, it is imperative to conduct studies with disease-free, healthy zebrafish. Based on 12 years of diagnostics performed by the Zebrafish International Research Center (ZIRC) and research conducted in the last cycles of this grant, we can conclude the following: Mycobacterium spp. and infections by Pseudoloma neurophilia (Microsporidia) are very common in zebrafish research laboratories. Some research facilities have experienced devastating mortalities in their zebrafish colonies due to infections by virulent Mycobacterium spp. Persistent, but less severe, infections by other mycobacteria and Pseudoloma have also plagued several facilities. The modes of transmission of these pathogens have been elucidated, and PCR-based diagnostic tests are available. However, little is known about how subclinical infections impact research endpoints, which is important now as several researchers are now using zebrafish as models in long-term studies on human pathogens, toxicology, aging and behavior. The major aim of the present study is to improve the health of zebrafish used in research facilities by investigating efficacy of disinfectants and antibiotics to reduce or eliminae infections. Evaluation of impacts of chronic infections by M. chelonae and Pseudoloma on fecundity, behavior, and cytokine profiles is another aim. Zebrafish that are immunsuppressed by gamma radiation are important models for human cancer studies, and investigate the impacts of underlying Pseudoloma infections in these fish will be studied. Results will be quickly distributed to the zebrafish community through through publications and the ZIRC web based manual on zebrafish.